1. Field of the Invention
The present invention relates to a method and apparatus for providing surge pressure reduction functionality while running a drilling/production liner or sub-sea casing down a borehole.
2. Description of the Prior Art
The principle of operation of a surge pressure reduction tool is described in U.S. Pat. No. 5,960,881 (xe2x80x9cthe ""881 patentxe2x80x9d), which is incorporated herein by reference and which should be referred to with respect to the advantages provided by that invention.
The invention of the ""881 patent has provided the oil well industry with the long-desired capability of running in a drilling/production liner or sub-sea casing faster and more reliably with a minimum of lost drilling fluid. Particularly, the surge pressure reduction tool comprises a housing assembly connected between a drill pipe and a drilling/production liner. The housing assembly includes a set of flow holes and an axial bore formed therein. A sliding sleeve resides within the axial bore of the housing assembly. When the sliding sleeve is positioned above the set of housing flow holes such that the sleeve does not block the flow holes, communication is established between the axial bore of the tool and the annulus between the tool and the borehole. This is called the xe2x80x9copen port positionxe2x80x9d and is established to facilitate surge pressure reduction when running a drilling/production liner through drilling fluid down a borehole. When the sliding sleeve is displaced axially downward such that the set of flow holes of the housing assembly is blocked, communication is interrupted between the axial bore of the tool and the annulus between the tool and the borehole. This is called the xe2x80x9cclosed port positionxe2x80x9d and is established to provide circulation of drilling fluid downward through the tool and to the bottom of the drilling/production liner without short-circuiting the flow of drilling fluid through the flow holes of the housing assembly. Additionally, the housing assembly contains a yieldable ball seat attached to the sliding sleeve to receive a drop ball to facilitate shifting the sliding sleeve axially downward from the open port position to the closed port position.
In operation, a drilling/production liner is run down a borehole using a drill pipe and a surge pressure reduction tool attached between the drill pipe and the drilling/production liner. Initially, the tool is set in the open port position to provide surge pressure reduction functionality while the tool is being lowered through drilling fluid down the borehole. As the drilling/production liner is lowered in the open port position, the drilling fluid flows upward through the drilling/production liner, into the tool, and outward into the annulus between the tool and the borehole via the flow holes. However, if the drilling/production liner encounters a tight hole or bridge condition within the borehole, then it is not possible to effectively circulate drilling fluid around the end of the drilling/production liner to help free it because the flow holes of the tool will short-circuit the flow of drilling fluid to the annulus outside the tool. Therefore, a drop ball is released into the drill pipe to land in the yieldable ball seat thereby effectively sealing the sliding sleeve. Drilling fluid pressure is then increased above the drop ball to shift the sliding sleeve axially downward into the closed port position. Drilling pressure is once again increased above the drop ball to push the ball through the yieldable ball seat and out of the bottom of the drilling/production liner. Drilling fluid can then be circulated from the drill pipe, past the surge pressure reduction tool, and through the drilling/production liner to free the drilling/production liner from the tight hole condition. Once the drilling/production liner is free, lowering of the drilling/production liner is continued until it reaches total depth.
At total depth, the surge pressure reduction tool must be in the closed port position to facilitate hanging and cementing operations. Therefore, if the drilling/production liner is run downhole without encountering a tight hole condition requiring the benefits of circulation, then the tool must be shifted to the closed port position once total depth is reached.
While the invention of the ""881 patent provides the oil well industry with much desired surge pressure reduction functionality, it only provides a single sequence of surge pressure reduction functionality per trip downhole. Therefore, once the tool has been shifted to the closed port position to facilitate circulation of drilling fluid to free the drilling/production liner from a tight hole condition, the drilling/production liner must be lowered the remainder of the trip to total depth without the benefits of surge pressure reduction.
Accordingly, a multi-function surge pressure reduction tool may be used to provide an additional sequence of surge pressure reduction per trip downhole. The principle of operation of a multi-function surge pressure reduction tool is described in U.S. application Ser. No. 09/812,522 (xe2x80x9cthe ""522 applicationxe2x80x9d), which is incorporated herein by reference and which should be referred to with respect to the advantages provided by that invention. The multi-function surge pressure reduction tool in accordance with the ""522 application includes a housing assembly with a set of flow holes formed therein and a valving sleeve with two sets of flow ports formed therein at different axial locations. When the set of flow holes of the housing assembly is aligned with either set of flow ports of the valving sleeve, the tool is in an open port position. When the set of flow holes of the housing assembly is not aligned with either set of flow ports of the valving sleeve, the tool is in a closed port position. Since the valving sleeve has two sets of flow ports, the tool can be shifted from a first open port position to a first closed port position, from the first closed port position to a second open port position, and from the second open port position to a second closed port position. Therefore, if the drilling/production liner being lowered downhole using the multi-function surge pressure reduction tool encounters a tight hole condition, the valving sleeve is shifted from the first open port position to the first closed port position. This permits circulation of drilling fluid to free the drilling/production liner from the tight hole condition. Then, the valving sleeve is shifted to the second open port position to provide surge pressure reduction functionality to the drilling/production liner for the remainder of the trip to total depth. Once the drilling/production liner reaches total depth, the valving sleeve is shifted downward to the second closed port position such that hanging and cementing operations may be commenced.
While the surge pressure reduction tool of the ""881 patent and the multi-function surge pressure reduction tool of the ""522 application provide a mechanism having surge pressure reduction functionality, it has been observed that circumstances may be encountered during the running downhole of a drilling/production liner where a tool in accordance with the ""881 patent or the ""522 application may be rendered ineffective to facilitate circulation and cementing operations. Particularly, if a drilling/production liner, while being lowered down the borehole, becomes plugged with drill cuttings and debris that were created and left in the borehole during drilling operations, then it may not be possible to shift the sliding sleeve downward into the closed port position. Therefore, with the sliding sleeve unable to shift out of the open port position, cementing operations can not be performed at total depth and circulation operations can not be performed if the drilling/production liner encounters a tight hole condition. This is due to a pressure build-up in the drilling fluid trapped between the yieldable ball seat sealed by the drop ball and the debris blocking the drilling/production liner. This pressure build-up causes a hydraulic lock condition in which the trapped drilling fluid resists the force exerted above the drop ball to shift the sliding sleeve axially downward. Therefore, the tool cannot be shifted out of the open port position and communication between the surface and the drilling/production liner via the drill pipe is short-circuited by the open flow ports of the tool.
Accordingly, the oil well industry would find desirable a surge pressure reduction tool that can be shifted to the open port position to provide surge pressure reduction and to the closed port position to facilitate cementing operations and circulation of drilling fluid even in the event that the drilling/production liner becomes plugged with drill cuttings or downhole debris.
In accordance with the present invention, a method and apparatus for reducing surge pressure while running a tubular member on a drill pipe with a running tool through drilling fluid down a borehole using a drilling rig is provided.
Apparatus in accordance with the present invention includes a diverter device having a housing assembly with a set of flow holes formed therein. The housing assembly is suspended from a drill pipe such that the drill pipe provides a communication conduit between the drilling rig on the surface and the borehole. The diverter device also includes a sliding sleeve positioned within the housing assembly. When the set of flow holes of the housing assembly is not blocked by the sleeve, the tool is in an xe2x80x9copen port position.xe2x80x9d When the set of flow holes of the housing assembly is blocked by the sleeve, the tool is in a xe2x80x9cclosed port position.xe2x80x9d
Apparatus in accordance with the present invention also includes a volume compensation device connected between the drilling/production liner and the diverter device. The volume compensation device, when activated, accumulates a volume of drilling fluid which is equal to or greater than the volume of drilling fluid displaced when the sliding sleeve moves from the open port position to the closed position.
In a preferred embodiment, the volume compensation device includes a housing having an upper end and a lower end and an axial bore formed therethrough. Additionally, the housing includes a set of annulus flow ports formed therein near the upper end. The volume compensation device also includes an inner sleeve having an upper end and a lower end, and an outer diameter smaller than the diameter of the axial bore of the housing. The total length of the inner sleeve is less than the length of the axial bore of the housing. The inner sleeve is arranged within the axial bore of the housing, and the upper end of the inner sleeve is attached to the upper end of the housing to form an annulus between the inner sleeve and the housing. An annular piston having an inner diameter approximately equal to the outer diameter of the sleeve and an outer diameter approximately equal to the diameter of the axial bore of the housing is attached to the lower end of the sleeve by at least one shear pin. If the drilling/production liner becomes plugged with drill cuttings or downhole debris, then trapped drilling fluid pressure within the volume compensation plug applies an upward force against the annular piston such that the set of shear pins shear and the annular piston moves axially upward. This provides the apparatus of the present invention with additional volume as required to shift the diverter device to the closed port position.
Furthermore, in the closed port position, apparatus in accordance with the present invention provides a flow path for drilling fluid to flow downward from the drill pipe to the diverter device, from the diverter device to the volume compensation device, from the volume compensation device to the running tool, from the running tool to the tubular member, and from the tubular member out into the borehole. Providing this flow path facilitates circulation and cementing operations.
Still furthermore, in the open port position, apparatus in accordance with the present invention provides an alternative flow path for drilling fluid to flow upward from the borehole into the tubular member, from the tubular member to the running tool, from the running tool to the volume compensation device, from the volume compensation device to the diverter device, and from the diverter device out into an annulus between the drill pipe and the borehole via the set of housing flow holes. Providing this flow path facilitates surge pressure reduction when lowering the tubular member downhole through drilling fluid.